When gases are administered, through a face mask, a valve is used which allows gas flow to take place through the mask into the patient's lungs, and when the patient exhales, the valve reverses and exhaled gas flows out to atmosphere. The patient may be unable to breath at all, or may be breathing spontaneously but with difficulty. The valve must therefore be capable of permitting spontaneous breathing, and also capable of permitting an assistant to carry out resuscitation.
One form of such a valve is shown in U.S. Pat. No. 4,071,025.
Equipment of this type is frequently used by paramedical personnel, nursing assistants, first aid workers, firemen, and service personnel. Such equipment is frequently required in an emergency, and in situations where malfunction of the equipment can occur for various reasons. For example, the gas supply can become blocked, due to a bend in a gas supply pipe for example. Similarly, a person being resuscitated is likely to vomit, and the vomit will enter the mask and may enter the valve itself.
Numerous other emergencies can also occur.
In many of these situations the result is that the valve becomes blocked, or gas flow from the gas supply into the valve is cut off.
In these situations, the assistant administering the gas may be distracted, and may not notice what has occurred. The patient is then in danger of suffocating.
Accordingly, it is desirable to provide in such a valve a means whereby in the event of a breakdown in the gas supply for any reason, atmospheric air is admitted to the valve, so that the patient can continue breathing.
Usually, the blocked valve or blocked gas supply condition will last only a few seconds at most, depending upon the experience of the assistant administering the gas. Once the assistant notices the problem, the mask is then quickly removed and either the valve must be dismantled and washed out, or the blockage in the supply must be cleared, and the valve and mask are then reassembled to continue treatment.
Again, these functions are done in an emergency situation, in many cases by persons who are not completely familiar with the way in which the equipment is designed.
When such valves are dismantled, the reassembly of the valve, if it involves many parts, may present serious problems. These problems will of course be greatly aggravated by the urgency of the situation. For all of these reasons therefore the design and fabrication of such valves becomes of critical importance to the success of the treatment. It is thus essential that the valve should be capable of providing the functions of gas inhalation, exhalation, and atmospheric air inhalation in the event of failure.
It is also essential that the valve shall have a minimum number of separate components, and that it may readily be disassembled, cleaned and reassembled by untrained personnel who are not familiar with the equipment. The valve must also be made of parts which are so arranged that it is impossible for the assistant to reassemble them in the wrong manner.
A somewhat improved form of valve is shown in Canadian Letters Patent No. 798,660. The valve shown in that patent involves two separate flexible valve members. One valve member opens to permit inhalation of gases, while the other valve member closes against the introduction of atmospheric air. On exhalation, the inlet valve moves away, and the exhalation valve opens up, allowing exhaled air to escape to atmosphere.
This type of valve is of a much simpler construction than that shown in earlier patents. However, it still does not provide for inhalation of atmospheric air in the event of a breakdown in the supply of gas. Consequently, although this form of valve can be cleaned and put back into service more easily than earlier forms of valve, in the event that it becomes clogged or blocked, it does not provide for the situation where the assistant who is administering the gas fails to notice that the gas supply has been cut off.
If in fact this should occur, and the gas supply becomes blocked for some reason, the patient will be unable to inhale atmospheric air, and will essentially suffocate quickly unless the mask is immediately removed.
Throughout this description, reference is made to the administering of a gas to a patient. It will of course be appreciated that the gas may be either pure oxygen, or air enriched with oxygen or ambient air, or a specially formulated mixture of gases.
In many circumstances where for example resuscitation is carried out in an emergency, special gases and oxygen supplies will not be available. In these cases, resuscitation is carried out simply by administering air by means of a manually operable bag. Numerous examples of such bags are shown in the prior art. One form of such bag is shown in U.S. Pat. No. 3,363,833. This form of bag is suitable for administering air alone, and may also be connected to a gas supply, so that it can be used for administering a gas.
For the purposes of this discussion therefore when reference is made to the administration of a gas, the term "gas" includes any mixture which may be breathed, including fresh air, oxygen, oxygen enriched air and specially formulated mixtures.